Richard and Anne Andalfinger wear matching Han Solo and General Leia Organa costumes – complete with a photo of the characters' son Kylo Ren – from "Star Wars: The Force Awakens" at Comic-Con at the San Diego Convention Center in California on July 21. The couple, both in their early 60s, have been going to conventions around the country for years. They say they now prefer smaller ones like Phoenix and Salt Lake City, where fans still run the show.

SAN DIEGO, Calif., and Boston — For Steven Bustamante, fantasy has long been serious business.

Now, as the computer repair technician's beloved genre – along with superhero stories and science fiction – takes over American pop culture, Mr. Bustamante sees that more people are tolerating and even embracing his long-held opinions.

"Ten, 15 years ago, you would never see a kid in a Captain America T-shirt," says Bustamante, sweating in the fur capes and leather vest of a northerner from the HBO fantasy series, "Game of Thrones" – his outfit for Day 1 of this year's Comic-Con. "Now you're seeing it more mainstream, happening almost every day."

Indeed, genres that once may have been viewed as only for outsiders are now the inspiration for some of the highest-grossing films of the year and some of the highest-rated TV shows.

The change is reflected in San Diego’s Comic-Con International, a yearly event that celebrates comic books, fantasy, and science fiction. The first three-day event was held in 1970 for about 300 people. Today, participants arrive in the tens of thousands to see studios like Disney and Warner Bros., TV networks like CBS, and streaming services like Netflix present projects.

"I think [the culture has] definitely changed, because ... there's not a child and for that matter not an adult who didn't grow up loving 'Star Wars,' then 'Star Trek' movies and more recently now, ['The Lord of the Rings'] and ['Harry Potter']," says Paul Levinson, professor of communication and media studies at Fordham University and author of the novel "The Plot to Save Socrates.”

"So many millions and millions of people have become fans of that – no one can use [the term 'geek'] in a dismissive, derogatory way."

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How did we get to the point where all things nerdy dominate pop culture to such an extent? And as studios like Marvel and Warner Bros. schedule movies into 2019 and “Harry Potter” kicks off a new franchise, can these projects continue successfully at such a pace? Is there such a thing as "peak geek?"

As to how it all began, culture experts say one film changed everything: a 1977 story about a galaxy far, far away.

“Up until 'Star Wars'… as far as movies were concerned, with a few exceptions ... science fiction was considered a very specialized niche,” Professor Levinson says. “It was not considered something that the mass public would be interested in.”

"Well, 'Star Wars' broke all that open.”

The fantasy genre then delivered a one-two punch in the movie industry with the 2001 releases of the films “The Lord of the Rings: The Fellowship of the Ring” and “Harry Potter and the Sorcerer’s Stone.”

“They did for fantasy what 'Star Wars' did for science fiction,” Levinson says.

A similar evolution has taken place for comic book adaptations. Where once they were the sole domain of introverted teens with overactive imaginations, caped crusaders today have acquired an aura of mainstream cool – as some who attended Comic-Con this year can attest.

Standing in a snaking line outside the San Diego Convention Center before doors opened on Thursday, Stephen Barnes of Fresno, Calif., recounts how his now-adult son had a tough time in high school because of his love for “geek” culture.

“He's a computer geek. He wasn't quite into sports and stuff like that, so he struggled then," Mr. Barnes, who is in his 50s, says. "Now ... everybody wants to talk to him because he's the man in the know."

Nifer, a 25-year-old Comic-Con attendee from San Francisco who declined to give her last name, says her parents still don’t seem to understand the new popularity of these properties – but her friends sure do.

“My parents certainly don't get it,” she says, waiting in line behind Barnes. “If I refer to myself as a nerd or a geek, they go, 'Isn't that like a negative term?' But ... I don't think any of my peers see it that way.”

In some cases, the warmer attitude toward those who consider themselves "geeks" has even given way to a level of awe.

"It's definitely different," says Bustamante, the cosplayer. When he talks to others about how he dresses up to show his love for shows like "Game of Thrones," he says, the response is often positive.

"They're like, 'Wait, you do that? That is insane,'" Bustamante says. "And it's not like insane as in a bad way, but insane like, 'That is amazing!' "

Hayden Donze (left) and Steven Bustamante dress up as characters from the HBO series "Game of Thrones" at Comic-Con at the San Diego Convention Center in California on July 21. While the recent mainstream interest in science fiction and fantasy have made Comic-Con more commercialized, they say, it has also brought greater acceptance of those who have always been passionate about such genres.Jessica Mendoza/The Christian Science Monitor

Even industry insiders are seeing a change. At his booth at Comic-Con's illustrators' area, DC Comics artist Philip Tan explains how he has watched as lovers of the genre have been increasingly welcomed into the mainstream fold.

"People don't shy away either from considering themselves as a fan of certain things, or as passionate enthusiasts of certain things," says Mr. Tan, who been a professional comic book artist for more than 15 years. "And they don't judge other people as much as they used to.

“It creates less conflicts and divides," he adds. "And ... when people start to accept people that are not the same as themselves, that's a good improvement for everyone.”

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With books like “Game of Thrones” and characters like Deadpool now being adapted for TV and film, stories that may have almost been like their own secret to fans – a private password to help identify those who shared their interests – are now famous worldwide. Comic-Con's organizers say attendance has topped 130,000 in recent years.

Of course, there are downsides to the growing crowd that flocks to San Diego every summer.

Richard Andalfinger, who is in his 60s and attended this year's Comic-Con dressed as Han Solo in the most recent iteration of “Star Wars,” says the convention has become “a little too commercial.”

“It's more of an industry trade show than a fan show at this point,” Mr. Andalfinger, who is attending for the 10th time, says. He and his wife Anne hail the more organic nature of smaller conventions in Phoenix, Ariz., and Salt Lake City where they say the fans still run the show.

"It was a lot of fun," says Anne, whose Leia Organa Solo outfit came complete with a set of tissues and a framed photo of villainous son Kylo Ren, played by Adam Driver. "They're much more into cosplay. More so than here."

"There's a lot of lines to get a ticket to get in line," adds Nurit Ambrose, a human resources manager rocking a homemade, knitted Supergirl costume. "It's incredible. There's a lot of people."

As she eyeballs a wall of fan-designed T-shirts, Ms. Ambrose, who is in her 30s, muses over the changes that have come over Comic-Con in the decade she has participated.

"It used to be a lot more about comic books and comics and anime and that. And now a lot of it is about, you know, the next awesome movie that's coming out," she says. After a pause, she adds, "Is there something between a con and a pro? I guess it's just what it is."

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For the most part, though, longtime con-goers seem to possess a "the more, the merrier" attitude about the craziness of Comic-Con – with the caveat that pop culture's newfound affair with all things geek is an authentic one, with lasting power.

"Hopefully not only are [people] getting the t-shirt, but they also like the character behind that t-shirt," Bustamante says. "It's not like, 'Oh yeah, I really like that design.' I hope you're doing something with the actual character, you know. That they kind of just delve in more."

“I think the more people who love what I love, the more people I get to share it with and talk about it with, and be excited about it with, the better,” Nifer says. “The more people who love this kind of content, the more of this kind of content gets created.”

Attendees browse through fan designed T-shirts at the San Diego Comic-Con in California July 21.Jessica Mendoza/The Christian Science Monitor

And the major studios appear to agree. Marvel Studios has scheduled movies into 2019, while Warner Bros., which releases films based on DC Comics properties such as next month's “Suicide Squad,” also has a slew of superhero films in the works. At Comic-Con, Netflix revealed new information about upcoming Marvel superhero TV shows “Luke Cage” and “Iron Fist,” while DC TV properties “Gotham” continues on Fox, and "Flash" and "Green Arrow" make their home on CW.

While it never went away, “Star Wars” blasted to new relevance in pop culture with the release of 2015’s “The Force Awakens,” which is now the highest-grossing movie domestically of all time (without adjusting for inflation). Multiple new films, including spin-offs, are planned. Meanwhile, a new series set in the “Harry Potter” world will kick off later this year with the upcoming film “Fantastic Beasts and Where to Find Them.”

Whether or not audiences will tire of the fare remains to be seen, but Levinson and others say sci-fi, fantasy, and the like are probably here to stay.

“It’s not going to go away,” he says, noting that while Westerns have declined in popularity, a cowboy movie is still sure to pop up every so often. “I don't think that science fiction and fantasy's ever going to go away completely. But I also do think that everything has its rise and its fall."

If the spirit of this year's Comic-Con is anything to go by, the "geek" genres may have quite a bit of shelf life yet. And in the meantime, fans are going to make the most of the experience.

"I've loved this stuff since I was a kid," Nifer says, grinning. "I think what it circles back to is if we're all having fun, I don't really care."